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Redliner: I watched that video before. I changed a few hoses that were bad. I see a hose deep behind that pressure sensor/secondary air pump(not sure if cracked). Does that go to vacuum system? Is this the one he is talking about in the video?

Noodles: I replaced the EGR with a new unit and cleaned the pipe reaallly well. Where the egr is connected to the exhaust, i did not clean. I do not see any smoke anywhere. Do you think i need to clean this? Can i just take thee egr off again and spray down there? If you have instructions i would really appreciate it.

Is there anything else that would make p0400 show up?

O yeah on a side note, i did clean the breather and reseal on the passenger side valve cover. I did not do the driver side. Is this a possibility?

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I wish this was a possible solution, but I had that same eng but in '99, and same code. Never figured it out... Solution was to get rid of the car.
I can only recall three car problems in my life that I could never figure out, this was one. Another was also a Benz with that same eng, same year as yours where it would die when put in gear until warmed up. Dealer couldn't figure that out either. Solution was to feed it hot air piped from the ex manifold via a clothes dryer duct. the eng didn't need to be hot, it just needed hot air! The other was driveshaft vibration (not Benz) that I dragged around with me for 20 years despite changing out so many parts over the years that it was literally a different vehicle. Now, several years later, the exact same vibe reappeared in my latest Benz.... Like before, everything looks/feels perfect, yet there it is. So while I love Benz overall, they can vex me and I may have to get rid of this one too.
Btw I scoured the web and every local Benz shop and dealer for a solution to the p0400 issue, which was in fact working perfectly. The dealer claimed to have never seen the issue, but I've heard that all my life about anything I have problems with. The dealer could not even tell me what in the programming trips p0400 so basically zero clues where to look other than what seems obvious.
If you find it, please post so others in that situation have something to go on. Best of luck to you...

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Interesting, thank you. Question. I initially had the p0171 code for secondfary air pump. When i went to check this code i found a broken piece of vacuum line between the air pumps (i think this is what they are called) and replaced. It made that code go away and thats when this p0400 showed up. Do you think it could be the air pumps? Is there a way to test these?

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There is only one AIR pump. It is in the center at the top front of the engine. If the P0171 code has not vom back then it is fine.
One or both of the exhaust ports that receive air from the pump is more than likely blocked. It is a know issue with the M112 V6 and M113 V8 engines.

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I had the same code on a 96 c280. I was having hard time trying to fix it. I then used the mercedes diagnostic socket and got a different code-I dont remember right now but it was the rear 02 sensor=reading to high. I replaced the sensor and all is good now. I did ohm the old sensor and sure enough the 12v power supply for the heater was shorted to the 02 signal wire and ecm ground, I compared readings to the new sensor and there should be NO connection-NO ohm reading.

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I had the same code on a 96 c280. I was having hard time trying to fix it. I then used the mercedes diagnostic socket and got a different code-I dont remember right now but it was the rear 02 sensor=reading to high. I replaced the sensor and all is good now. I did ohm the old sensor and sure enough the 12v power supply for the heater was shorted to the 02 signal wire and ecm ground, I compared readings to the new sensor and there should be NO connection-NO ohm reading.

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Did it happened to some of you?
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The back...

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I have a 2006 R500. The esp light has been intermittently coming on for about 2 months. Usually after driving, shut off, and driving again. It would come on right away for about 5 or 6 miles. The stereo also has been intermittently not working. The Nav works, but theres no audio. And the 6...

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